During the production of foodstuffs, such as milk (products), fruit juices, beer, soft drinks (such as lemonades), cider, wine, sherry, port, distilled drinks and the like, the problem often occurs that apparatus must be cleaned after a certain period, because components from the material to be treated are adsorbed or absorbed or precipitate on surfaces of the apparatus, which is undesirable. This may in fact give rise to a disturbance of, on the one hand, the operation of the apparatus and, on the other hand, the quality of the final product.
The apparatus involved is the apparatus used during the treatment of foodstuffs, more in particular liquids, as indicated above. More in particular, filters are involved, such as membrane filters used for filtering the above products or semimanufactures therefor.
Examples of such treatments are the production and/or processing of milk and milk products, fruit juices, beer, soft drinks, cider, wine, sherry, port, distilled drinks and the like.
In the case of brewing beer the invention relates to, inter alia, the apparatus used during the preparation of malt, the conversion of malt and/or unmalted grain into wort and the further processing of the wort, with or without addition of extra components, such as hops, by fermentation to beer, as well as all auxiliary apparatus used therewith and coming in contact with main or secondary streams from these processes.
An example of the disturbance of the operation of the apparatus is found with the different filters used, e.g. the filters for filtering soft drinks, milk (products), wine, sherry, port, distilled drinks, fruit juices, lemonade, beer, such as settled beer, residual beer, but also the wort/spent grain separation, hot trub separation and cold trub separation.
The capacity of filters used in such processes, the flux, decreases in the course of time, which is of course undesirable. This particularly plays a role when use is made of membrane filters. This capacity decrease can be partly inhibited by rinsing back the filter. After some time, however, this is not sufficient, and it is therefore necessary to clean the filter.
A further examination has revealed that the apparatus, and more in particular the filters, become contaminated by a combination of all kinds of compounds, of which polysaccharides, oligosaccharides, proteins, .beta.-glucanes, fats and polyphenols are important components. during the production
Conventional cleaning techniques, e.g. based on catalyzed or uncatalyzed oxidation, e.g. with a peroxide/metal (manganese) complex hypochlorite or hypobromite, are not satisfactory, which appears from the fact that the flux cannot be restored to the original value or close thereto. Nor does the use of detergents or enzymes, such as proteases, carbohydrases, amylases, pullulanases, proteases and lipases, lead to the desired results.
There is therefore a need for an efficient cleaning system for cleaning apparatus for the production, as defined above, of liquid foodstuffs, which system is capable of effecting a proper cleaning, which must preferably be done within a short time (15-120 min) and during which substantially all contaminations are removed.
The invention is based on the surprising insight that it is possible to adequately clean apparatus used during the production of foodstuffs by using a cleaning system on the basis of a combination of a cyclic nitroxyl compound and a hypohalite. This involves removal of contaminations formed during the production of foodstuffs, e.g. precipitated on surfaces of the apparatus or in pores of filters.